1. Field of the Invention
The present invention relates to an optical multiplex transmission apparatus and an optical multiplex transmission method, which enable each of a plurality of control nodes connected to a common optical multiplex transmission path to have its operation mode changed over to a multiplex communication mode wherein the control node performs multiplex communication through an interface for use on multiplex transmission, that is provided to this control node, and to a sleep mode wherein this interface is kept inoperative. More particularly, the invention concerns an optical multiplex transmission apparatus and an optical multiplex transmission method, which can be simplified by changing over the control node from the sleep mode to the multiplex communication mode without providing a wake-up signal electric wire.
2. Related Art
An optical multiplex transmission apparatus for performing multiplex communication has recently been loaded on a vehicle. This optical multiplex transmission apparatus is constructed by a plurality of control nodes being connected to a common optical multiplex transmission path such as an optical fiber.
Each control node has provided therein a multiplex communication interface for performing multiplexing of data and thereby performing transmission and reception thereof, whereby transmission and reception of data are done between microcontrollers provided in the respective control nodes through the multiplex interface and optical multiplex transmission path.
Also, in order to suppress the power consumption maximally, each control node has a change-over function for changing over the mode thereof to a multiplex communication mode for performing multiplex communication through the multiplex transmission interface and to a sleep mode for causing the multiplex transmission interface to be kept inoperative and thereby causing a decrease in the current consumption.
At an ordinary time, the control node is operated in the sleep mode to thereby suppress useless power consumption. When prescribed starting conditions have been satisfied, the mode of the control node is changed over, by a wake-up signal, to the multiplex communication mode in which the operational condition of the microcontroller is made xe2x80x9conxe2x80x9d through the multiplex transmission interface.
FIG. 1 is a block diagram illustrating the construction of a type of conventional optical multiplex transmission apparatus. In the optical multiplex transmission apparatus illustrated in FIG. 1, it is arranged that a master node 101 serving as a control node and a plurality of slave nodes 102a to 102n controlled by this master node 101 are connected in the form of a ring by an optical multiplex transmission path 103 (103a to 103n) such as an optical fiber, whereby a multiplex communication signal is transmitted in the direction indicated by the arrows.
It is to be noted that in each node Rx represents the reception of a multiplex communication signal and Tx represents the transmission of a multiplex communication signal. Also, a wake-up signal electric wire 104 for transmitting a wake-up signal from the master node 101 to the slave nodes 102a to 102n is provided.
As described above, the wake-up signal electric wire 104 is provided separately from the optical multiplex transmission path 103 that is a data transmission line. At the time of activation after turning on a main power source, a given node, for example, a master node 101, transmits a wake-up signal to all the slave nodes 102a to 102n through the wake-up signal electric wire 104. Upon receipt of the wake-up signal, each slave node 102a to 102n changes over the interface portion from the sleep mode to the multiplex communication mode.
In this way, every one of the slave nodes 102a to 102n is transferred from the sleep mode to the multiplex communication mode, and then bi-directional communication can be made between each node through the optical multiplex transmission path 103.
However, in the conventional optical multiplex transmission apparatus, although the slave nodes can be stably activated by using a wake-up signal, the wake-up signal electric wire had to be provided separately from the optical multiplex transmission path that is a data transmission line.
Providing this wake-up signal electric wire is due to the following reason. In the sleep mode, the current consumption is appreciably limited. Therefore, in a case where having used the optical multiplex transmission path, the power source of a light receiving portion must be made xe2x80x9coffxe2x80x9d in order that the apparatus may be in sleep mode.
For this reason, in order to activate from the sleep mode, as illustrated in FIG. 2, separately from optical interfaces (optical IFs) 106a, 106b of, for example, a light receiving portion, etc., the wake-up signal electric wire, i.e., electric interfaces (electric IFs) 107a, 107b were provided, whereby the apparatus was activated from the sleep mode by using a wake-up signal which is a kind of electric signal. Therefore, there was the problem that the wire reduction effect resulting from the multiplex communication was impaired. In addition, the wiring or distribution of the wake-up signal electric wire became complex or costly.
An object of the present invention is to provide an optical multiplex transmission apparatus and optical multiplex transmission method which enable the system to be simplified, and enable each control node to be activated and commence its communication, without providing any wake-up signal electric wire separately from a data transmission line.
To attain the above object, there is provided an optical multiplex transmission apparatus wherein a plurality of control nodes are connected to an optical multiplex transmission path; and each control node performs communication, through a multiplex communication portion for use in multiplex transmission that has been provided therein, with another control node, the each control node comprising: a light receiving portion that operates by having a power source signal supplied thereto and receives an optical signal from the another control node; a mode changing-over portion that alternately changes over the mode of the control node between a multiplex communication mode for performing multiplex communication and a sleep mode in which the multiplex communication portion is kept inoperative every prescribed period of time; and a light reception control portion that has alternately repeated therein a power source supply time length corresponding to the multiplex communication mode during which the power source is supplied and a power source non-supply time length corresponding to the sleep mode during which the power source is not supplied, and that produces a power source supply pulse signal wherein a duty ratio between the power source supply time length and the power source non-supply time length is preset and supplies the power source supply pulse signal to the light receiving portion, whereby when the mode changing-over portion changes over the mode of the control node from the sleep mode to the multiplex communication mode and the light receiving portion has received a light signal, the mode changing-over portion causes the multiplex communication mode to be maintained while the light signal is being received, and the light reception control portion causes the power source to continue to be supplied to the light receiving portion while the light signal is being received.
According to this invention, the multiplex communication mode and sleep mode are alternately repeated every prescribed period of time and the power source supply pulse signal having a preset duty ratio is supplied to the light receiving portion. Therefore, the current consumption that is made during the sleep mode is suppressed to a value that falls within a permissible range. Further, when the mode of the control node has been changed over from the sleep mode to the multiplex communication mode and the light signal has been received, the multiplex communication mode is caused to continue to be as is and the supply of the power source to the light receiving portion is caused to continue to be made, whereby it is possible to activate the control node from the sleep mode. This makes it unnecessary to provide a wake-up signal electric wire separately from the optical multiplex transmission path and therefore makes it possible to simplify the system.
In a preferred embodiment of the present invention, after the mode changing-over portion has changed over the mode of the control node from the sleep mode to the multiplex communication mode, the light reception control portion supplies the power source to the light receiving portion during, and by, the power source supply time length according to the power source supply pulse signal.
According to this embodiment, the light reception control portion supplies, after the mode has been changed over from the sleep mode to the multiplex communication mode, the power source to the light receiving portion during, and by, the power source supply time length according to the power source signal, with the result that it is possible to make the duty ratio low and so to decrease the current consumption.
In a preferred embodiment of the present invention, upon receiving no light signal from the other control node, the light reception control portion, before change-over from the multiplex communication mode to the sleep mode, stops the supply of the power source to the light receiving portion during, and by, the power source non-supply time length according to the power source supply pulse signal.
According to this embodiment, upon receiving no light signal from the another control node, the light reception control portion, before change-over from the multiplex communication mode to the sleep mode, stops the supply of the power source to the light receiving portion during, and by, the power non-supply time length according to the power source supply pulse signal. Therefore, the duty ratio can be made low and so the current consumption can be decreased.
In a preferred embodiment of the present invention, the optical multiplex transmission apparatus further comprises a multiplex communication control portion which determines whether the light receiving portion has received the light signal and, when the light signal has been received thereby, causes the supply of the power source to the multiplex communication portion and, when no light signal has been received thereby, stops the supply of the power source to the multiplex communication portion.
According to this embodiment, the multiplex communication control portion, when the light signal has been received thereby, causes the supply of the power source to the multiplex communication portion and, when no light signal has been received thereby, stops the supply of the power source to the multiplex communication portion. Therefore, since no current is caused to flow into the multiplex communication portion, it is possible to largely decrease the current consumption in a state prior to the start made from the sleep mode. As a result, since the duty ratio can be made high by the extent to which the current consumption of the multiplex communication portion has been able to be decreased, the activation responsivity becomes high.
In a preferred embodiment of the present invention, the multiplex communication control portion comprises: a reception determining portion for determining whether the light receiving portion has received the light signal; a switch for, when the light receiving portion has received the light signal, permitting the supply of the power source to the multiplex communication portion according to a control signal from the reception determining portion; and a gate for, when the light receiving portion has received the light signal, permitting the light signal output from the light receiving portion to be input to the multiplex communication portion according to the control signal from the reception determining portion.
According to this embodiment, when the light receiving portion has received the light signal, the power source is supplied to the multiplex communication portion and the light signal output from the light receiving portion is input to the multiplex communication portion. Therefore, since the duty ratio can be made high by the extent to which the current consumption of the multiplex communication portion has been able to be decreased, the activation responsivity becomes high.
In a preferred embodiment of the present invention, the plurality of the control nodes are connected to one another by the optical multiplex transmission path in the form of a ring.
According to this embodiment, the plurality of the control nodes are connected to one another in the form of a ring by the optical multiplex transmission path. Therefore, even when a part of the optical multiplex transmission path is broken, all of the control nodes can be activated if transmitting a wake-up signal in an opposite direction. Also, since in a ring type network each control node is sequentially activated from the sleep mode, there is the merit that if the activation responsivity in each of the individual control nodes becomes high, the activation responsivity in the entire network becomes also high.
Further, to attain the above object, there is provided an optical multiplex transmission method wherein a plurality of control nodes are connected to an optical multiplex transmission path; and each control node performs communication, through a multiplex communication portion for use in multiplex transmission that has been provided therein, with another control node, the method comprising the steps of: alternately changing over the mode of the control node between a multiplex communication mode for performing multiplex communication and a sleep mode in which the multiplex communication portion is kept inoperative every prescribed period of time; alternately repeating a power source supply time length corresponding to the multiplex communication mode during which the power source is supplied and a power source non-supply time length corresponding to the sleep mode during which the power source is not supplied, and producing a power source supply pulse signal wherein the duty ratio between the power source supply time length and the power source non-supply time length is preset and supplying the power source supply pulse signal to a light receiving portion; and causing a continuation of the multiplex communication mode during a reception of the light signal and causing a continuation of the supply of the power source to the light receiving portion during the reception of the light signal, when the mode of the control node has been changed over from the sleep mode to the multiplex communication mode and the light receiving portion has received the light signal.
In a preferred embodiment of the present invention, after the mode changing-over portion has changed over the mode of the control node from the sleep mode to the multiplex communication mode, the power source is supplied to the light receiving portion during, and by, the power source supply time length according to the power source supply pulse signal.
In a preferred embodiment of the present invention, when the light receiving portion receives no light signal from the other control node, the supply of the power source to the light receiving portion is stopped during, and by, the power source non-supply time length according to the power source supply pulse signal before change-over from the multiplex communication mode to the sleep mode.
In a preferred embodiment of the present invention, a determination is made of whether the light receiving portion has received the light signal and, when the light signal has been received thereby, the supply of the power source to the multiplex communication portion is made and, when no light signal has been received thereby, the supply of the power source to the multiplex communication portion is stopped.
In a preferred embodiment of the present invention, when the light signal has been received, the light signal output from the light receiving portion is input to the multiplex communication portion.
In a preferred embodiment of the present invention, the plurality of the control nodes are connected to one another by the optical multiplex transmission path in the form of a ring.
The nature, principle and utility of the invention will become more apparent from the following detailed description when read in conjunction with the accompanying drawings.